This method has been added in order to allow lnd to collect eligible
unspent witness programs outputs from the wallet controller for use as
inputs to the funding transaction.
Additionally, the change address functions now also specify whether the
generated change address should be payable to a witness program or not.
The WalletController will serve as a layer of separation between “base”
Bitcoin wallet logic, and the higher level Lightning Network logic. As
a result LightningWallet will no behave as an overly wallet, relying on
the lower wallet for basic services such as new address, signing etc.
Within this higher level lies the awareness of channel types, chain
monitoring, HTLCs, and so on.
